Within the sphere of the silicone water repellents used on fibers and fiber-based products, Japanese Published Patent Application (Kokoku or Examined) Numbers Sho 51-9440 (9,440/1976) and Sho 53-4158 (4,158/1978) teach silicone water repellents comprising methylhydrogenpolysiloxane, an aromatic or aliphatic hydrocarbon solvent (e.g., toluene, xylene, n-hexane, n-heptane), and a curing catalyst such as a platinum compound or an organotin compound. However, these silicone water repellents require heating at temperatures from 100 to 180.degree. C., which has a negative influence on production costs and which also limits the types of fibers and fiber-based products to which these water repellents can be applied.
In addition, fluoropolymers are known to have the ability to impart water repellency and staining resistance to solids and as a result are also frequently used in, for example, the leather and building material sectors and as surface treatment processing agents. These fluoropolymers are the polymers of a perfluoro group-functional or fluoroalkyl-functional polymerizable monomer or the copolymer of such a monomer with another polymerizable monomer.
When treating a solid such as a fiber-based product, leather, or building materials to impart water repellency thereto, the consuming public desires spray formulations to facilitate the application process. However, the efficient generation of water repellency by a spray process imposes various limitations on the composition of the water repellent.
Thus, the following prerequisites must be met: (1) the base or active ingredient of the water repellent must have an excellent affinity or compatibility with the propellant gas; (2) the base or active ingredient of the water repellent must dissolve in a homogeneous manner in the solvent in the water repellent; and (3) the water repellent, when sprayed on a solid, must readily wet the surface of the solid and must have a suitable infiltrability into the solid. When these conditions are satisfied, a uniform spray and an excellent water repellency and staining resistance are produced without the generation of powder ejection, fluffing, or whitening.
The consuming public also considers it of crucial import that spray-formulated water repellents be usable with a high level of safety and without the appearance of unpleasant odor. As far as these issues are concerned, the fluoropolymers referenced above are insoluble in low-toxicity alcohols such as ethanol, and the organic solvent used to dissolve the fluoropolymers must therefore be selected from among solvents such as ketones, e.g., acetone or methyl ethyl ketone, esters such as ethyl acetate, aliphatic hydrocarbons such as n-hexane and n-heptane, aromatic hydrocarbons such as toluene and xylene, and chlorinated hydrocarbons such as 1,1,1-trichloroethane and trichloroethylene.
Unfortunately, almost all of these solvents fail to satisfy any of the preceding prerequisites (1) to (3). In actuality the only solvent that can be used for the fluoropolymers is 1,1,1-trichloroethane. This solvent has, however, been implicated as a cause of depletion of the atmospheric ozone layer and its use is being increasingly restricted for purposes of global environmental protection. Thus, investigations have been carried out in pursuit of a solvent for the fluoropolymers that could replace 1,1,1-trichloroethane, but at present acceptable results have yet to be obtained.
The object of this invention is to provide a water repellent for treating solids that has the ability to impart a highly durable and robust water repellency to solids.